1. Field of the Invention
The present invention relates to an image processing apparatus that processes a moving image to be displayed on a liquid crystal display device, an image processing method and an image processing program.
2. Description of the Related Art
In recent years, liquid crystal display devices are used in many fields such as monitors for Personal Computer (PC), notebook PC, and television, and accordingly providing more opportunity to view moving images on liquid crystal display devices. Since, however, the response time of liquid crystal in the liquid crystal display devices is not fast enough, when a moving image is displayed, the deterioration of image quality such as blur and persistence of vision occurs. In general, since the refresh rate of the liquid crystal display devices is 60 Hz, a target response time is 16.7 ms or less in the display of moving images.
In order to improve the response time of the liquid crystal display devices, new liquid crystal materials with short response time are developed, and a method of driving the liquid crystal display devices using conventional liquid crystal materials is improved. As new liquid crystal display materials, smectic type ferroelectric crystal, antiferroelectric crystal and the like are developed, but they have a lot of problems, such as ghosting due to an influence of spontaneous polarization of liquid crystal materials and easy breakage of an orientation state in liquid crystal due to pressure or the like, which have to be solved.
On the other hand, as methods of driving liquid crystal display devices using conventional liquid crystal materials are improved, a method of writing to the liquid crystal display devices a gradation (enhanced gradation) to which predetermined gradation is added according to writing gradation when displayed gradation changes is proposed (for example, see Japanese Patent Application Laid-Open No. 2003-264846: Hereinafter, called as the first document) as a method of improving the response time of the liquid crystal display devices. According to the method in the first document, since the enhanced gradation is obtained by a comparatively simple calculation, a high-speed process can be executed by software.
The method in the first document, however, has a problem that an improving effect of the response time is insufficient between some gradations. For example, in a change from 0 gradation to 255 gradation, since the gradation of image data is generally 255 (8 bit) at the highest, the writing gradation cannot be enhanced. For this reason, the enhanced gradation is also 255, but in this case the response cannot be completed after one frame. In the structure proposed in the first document, when the device needs to obtain enhanced gradation of a next frame, the device calculates the enhanced gradation of the next frame assuming that the current frame has already attained 255, and thus distortion of the response waveform such as undershoot occurs. Such distortion of the response waveform in the liquid crystal display devices is visually recognized as a deterioration of moving images displayed on the liquid crystal display device.
The present invention is devised in order to solve the above problems and its main object is to provide an image processing apparatus, an image processing method, and an image processing program which reduce distortion of a response waveform of a moving image to be displayed on a liquid crystal display device by comparatively simple calculation and is capable of improving image quality.